05 Jan 2015:
U.S. Cities Are Significantly
Brighter than German Cities, Scientists Say
German cities emit several times less light per capita than similarly sized American cities, according to new research
published in the journal Remote Sensing
Berlin, Germany, at night
Moreover, the differences in light emission become more dramatic as city size increases: Light per capita increases with city size in the U.S. but decreases in Germany. Factors such as the type of lamps used and architectural elements like the width of the streets and the amount of trees are likely behind the differences, the researchers say. Energy-efficient LED street lighting
is currently being installed in many cities worldwide, and the researchers expect this to change the nighttime environment in many ways — for example, by reducing the amount of light that shines upward. The study also found that, in major cities in developing countries, the brightest light sources were typically airports or harbors, whereas the brightest areas in large European cities are often stadiums and city centers.
23 Dec 2014:
Madrid Announces Largest
Energy-Efficient Street Lighting Project
The city of Madrid has announced plans
to renew its entire street lighting system with 225,000 new energy-efficient
New energy-efficient street lighting in Madrid, Spain.
bulbs, the world’s largest street-lighting upgrade to date. The new lights, which will afford the city a 44-percent reduction in energy costs, will pay for themselves, according to Philips
, the company supplying the new system. In addition to drawing less overall power, the bulbs’ intensity will be controlled from a central command panel, resulting in less wasted energy. Of the 225,000 new lights, 84,000 will be locally manufactured LEDs, and the city is taking measures to ensure the safe recycling of heavy metals found in the old lamps. Similar, though smaller, projects have been undertaken in Argentina, Sweden, and the Netherlands.
25 Nov 2014:
China’s Lake Ebinur Has Been
Shrinking Dramatically, NASA Image Shows
As this NASA satellite image shows
, Lake Ebinur, located in northwestern China near the border of
Kazakhstan, has shrunk by 50 percent since 1955 as a result of development, agriculture, and natural fluctuations in precipitation. The lake’s saline water is light blue, and the dried lake bed appears white due to salts and other minerals that have been left behind as the water evaporates. The lake’s size fluctuates from year to year due to natural variations in snowmelt and rainfall, and human activity also plays a key role, Chinese researchers say. The nearby city of Bole, with a population of 425,000, consumes significant amounts of water, and farmers irrigate their crops — especially cotton — with water that would otherwise flow into the lake, researchers say. Frequent saline dust storms contribute to desertification, damage soils, harm wetlands, and may be hastening the melting of snow and glaciers downwind, researchers say.
06 Oct 2014:
Number of Megacities Has
Nearly Tripled Since 1990, UN Report Says
The number of urban areas with more than 10 million inhabitants — sometimes called "megacities" — has
nearly tripled in the last 24 years, jumping from 10 in 1990 to 28 in 2014, according to the latest UN report on world urbanization
. The total number of people living in megacities has grown from 153 million to 453 million during that period, the report says, and such areas now account for 15 percent of global GDP. Although densely populated urban areas can be environmental blights, innovations in efficient transportation have arisen from some major cities in Asia and Lagos, Nigeria, because those cities have invested heavily in public transit infrastructure, researchers say
15 Sep 2014:
Urban Air Pollution May
Affect Brains of Young Children, Study Says
Children living in areas with high air pollution are at increased risk for brain inflammation and for developing
Smog over Mexico City
neurodegenerative conditions such as Alzheimer's and Parkinson's disease, according to
a study by researchers at the University of Montana. The scientists compared brain and spinal fluids of children living in low-pollution areas to those of children living in Mexico City, an area notorious for its poor air quality. They found that children living in the city had significantly increased levels of combustion-related metals in their systems, as well as higher levels of antibodies related to inflammation. The antibodies are an indicator of autoimmune response and are possibly tied to higher risks for neurodegenerative conditions such as Alzheimer's and Parkinson's disease, according to the researchers. They say that a study following the Mexico City children as they age is needed to determine whether there is a relationship between their autoimmune responses and documented brain and cognition changes.
05 Sep 2014:
Smog in India Damaged
Enough Crops to Feed 94 Million, Study Says
Ground-level ozone, the main component of smog, damaged 6.7 million tons of Indian crops worth an
Smog in Delhi, India
estimated $1.3 billion in a single year, according to
a new study published in Geophysical Research Letters
. That's enough wheat, rice and other staple crops to feed 94 million people — roughly one-third of the country's impoverished population. Arising from a combination of vehicle emissions, cooking stoves, and industrial sources, plant-damaging ozone has left many of India's fast-developing cities among the most polluted in the world, according to the country's Air Monitoring Center. The number of vehicles there has nearly tripled in the past 10 years, rising from 50 million in 2003 to 130 million in 2013, and the country currently has no air quality standards to protect crops from ozone pollution. The researchers say the findings should be used to guide new ozone emission standards for the country.
26 Aug 2014:
Meat Production, Especially
Beef, Strains Land and Water, Study Says
Global meat production has expanded more than four-fold over the last 50 years — and 25-fold since
Beef cattle graze in Colombia
1800 — due to growing purchasing power, urbanization, and changing diets, according to a new report from the Worldwatch Institute
. Consumers in industrial countries still eat much larger quantities of meat (75.9 kilograms per person) than those in developing nations (33.7 kilograms), though that gap is beginning to close, the report says. Nearly 70 percent of the planet's agricultural land and freshwater is used for livestock, with additional land and water used to grow grains for livestock feed. Beef production alone uses about three-fifths of global farmland and yields less than 5 percent of the world's protein, according to the report. Sustainable agricultural practices
such as feeding livestock with grasses instead of grains and using natural fertilizers could reduce these impacts, the report notes, but alternative dietary choices hold the most immediate promise for reducing the environmental footprint of meat production.
04 Aug 2014:
California Takes Steps to
Curb Lawn Watering During Severe Drought
In the midst of a severe, long-term drought, California is taking unprecedented steps to discourage watering of
A drought-resistant yard
residential lawns, with some areas offering residents substantial cash incentives for installing water-saving landscaping, AFP reports
. The "Cash in Your Lawn" program in Los Angeles offers residents up to $6,000 ($3 per square foot) for replacing their lawns with drought-tolerant plants, rocks, and pebbles. Throughout the state, Governor Jerry Brown recently prohibited lawn watering more than two times per week and banned fines for brown lawns, which homeowner associations sometimes impose with the intent of improving a neighborhood's appearance. The drought, currently in its third year, threatens the water supply of California's 38 million residents. Agricultural regions
have already seen severe water reductions, placing extra pressure on the state's groundwater reserves.
22 Jul 2014:
Costs of Urban Light Pollution
Highlighted in Citizen Science Effort
A recently launched citizen science
project aims to highlight the environmental, social, and financial impacts of excessive nighttime lighting in cities around
the world. The project, called Cities at Night
, enlists people to help identify the cities pictured in thousands of blindingly lit photos taken by astronauts orbiting the earth. Organizers hope that when residents and officials see the bright photos of their cities at night, they will be prompted to cut nighttime light use and energy consumption. Widespread artificial lighting has made light pollution
a growing problem in urban areas by disrupting behavioral patterns of people and wildlife, wasting millions of dollars in energy costs, and adding greenhouse gases to the atmosphere. Some solutions are relatively inexpensive and straightforward, the organizers say, such as using shields to direct light down to street-level, which can allow a city to use lower-wattage streetlights.
03 Jul 2014:
Human Activity Has Boosted
Plant Growth Globally, NASA Data Show
On a global scale, the presence of people corresponds to more plant growth, according to
an analysis of three decades of global vegetation greenness data from
Agriculture has increased global vegetative cover.
satellites. More than 20 percent of global vegetation change can be attributed to human activities, such as agriculture, nitrogen fertilization, and irrigation, rather than climate change, researchers report in the journal Remote Sensing
. The findings suggest that global climate change models, which typically don't consider human land use, should take into account the relatively large impact human settlements can have on vegetative cover, the researchers say. From 1981 to 2010, areas with a human footprint saw plant greenness and plant productivity increase by up to 6 percent, while areas with a minimal human footprint, such as rangelands and wildlands, saw almost no change. Most increases in growth and greenness were seen near rural areas and villages, where agriculture is more intense.
09 Jun 2014:
Air Conditioning Can Raise
Urban Nighttime Temperature by 2 Degrees
Excess heat from air conditioners raises outdoor temperatures at night by nearly 2 degrees F (1 degree C), worsening the urban heat island effect and increasing cooling demands, according to research
from Arizona State University. Studying the Phoenix metropolitan area, researchers found that air conditioning systems pumped more waste heat into the air during the day, but the effect on near-surface temperatures was negligible. The same was not true for nighttime temperatures, however, when waste heat significantly boosts air temperatures because of nighttime atmospheric conditions. Air conditioning systems can consume more than 50 percent of total electricity
during extreme heat, the researchers note, and summertime extreme-heat days are projected to become more frequent and intense as a result of climate change. Redirecting waste heat from air conditioning systems to household appliances such as water heaters, for example, could help alleviate the problem, the scientists say. They project that such strategies would save at least 1,200 to 1,300 megawatt-hours of energy per day in the Phoenix metropolitan area alone.
Interview: Putting San Francisco
On the Road to Zero Waste by 2020
For 20 years, Jack Macy has spearheaded San Francisco’s efforts to become a global leader in recycling. In an interview with Yale Environment 360
Macy describes how San Francisco has succeeded in reusing or composting 80 percent of its garbage and how the city has engaged the public in a recycling crusade, allaying initial fears of “trash police” sifting through residents’ garbage. While San Francisco has made tremendous progress, Macy says further changes are needed. “Part of the principle of zero waste is that the local government can’t shoulder all the burden,” he says, “so it’s important that we encourage consumers to take responsibility for what they buy ... and producer responsibility for the products they design and market.”
05 May 2014:
New European Satellites
To Give More Detailed Views of Earth
The European Space Agency has begun launching
a series of satellites designed to collect detailed environmental data around the globe — from radar-based, high-definition imagery to information about the
atmosphere's chemical composition. The first satellite in the ESA's Copernicus program, the Sentinel 1A, was launched last month and has already returned many striking images based on radar data, such as this view of Brussels, Belgium, in which the dense urban area contrasts with the city's heavily vegetated surroundings. Once Sentinel satellite 1B is launched next year, the two will be able to map the entire globe in six days, giving researchers and conservationists a powerful way to monitor both short- and long-term changes in the environment. Four additional groups of satellites are set to launch this year. Those arrays will focus on high-resolution photo imagery, topography, surface temperatures, and atmospheric chemistry.
10 Apr 2014:
Mapping Program Helps
Cities See Money Saved by Planting Trees
New open-source software is helping cities better understand the benefits trees provide by calculating the value of the trees' ecosystem services, such as air quality improvements and CO2 storage. More than a dozen
cities have undertaken tree inventory initiatives, thanks to the OpenTreeMap software
, and residents have helped map more than 1.1 million trees worldwide. In addition to plotting a tree's location, users record its size, species, and other parameters that allow the software to calculate the tree's ecological value in terms of dollars saved through such benefits as cleaner air. San Diego's more than 340,000 mapped trees
, for example, are estimated to provide the city more than $7 million in benefits each year, including $4 million in air quality benefits and $2 million in reduced energy costs. In the coming months, the software will allow city managers to decide where to plant trees for maximum environmental benefit.
08 Apr 2014:
'Living Fences' Dramatically
Cut Livestock and Lion Killings in Tanzania
A novel, low-tech idea is helping Tanzania's lion population rebound: So-called "living fences" — which enclose livestock and are constructed of actively growing trees and chain-link fencing — have cut lion
A Masai villager installs a living fence.
attacks and retaliatory killings by more than 85 percent in the areas they've been installed, the Guardian reports
. Traditionally, the Masai have built livestock enclosures out of thorny acacia trees, but those fences are relatively fragile. Chain-link fencing alone is more durable, but leopards and small lions can scale the fences, and hyenas can tunnel in below. By interweaving actively growing African myrrh trees with the chain link fencing, the Masai have created a barrier that lions can't climb over, and their root systems prevent predators from digging under the fence. Because livestock predation has been cut, communities that had been killing six or seven lions annually now kill, on average, less than one, leading to a rebound in lion populations.
01 Apr 2014:
Delaware River Watershed
Is Focus Of Large-Scale Restoration Project
A Philadelphia foundation is providing $35 million to launch a host of programs aimed at better protecting the Delaware River
, which flows through the heart of
Delaware River at Trenton, New Jersey
the populous U.S. eastern seaboard and provides drinking water for 15 million people. The William Penn Foundation, working with nonprofit groups such as The Open Space Institute, says its Delaware River Initiative will protect more than 30,000 acres of land, launch 40 restoration projects, create incentives for businesses and landowners to protect the watershed, and set up a comprehensive program of water quality monitoring that will enable the foundation and its partners to measure the success of their programs and the overall health of the river. A cornerstone of the foundation’s initiative will be its restoration and protection work in eight so-called “sub-watersheds” that feed into the Delaware River.
24 Mar 2014:
Ride-Sharing Could Cut Taxi
Trips by 40 Percent in NYC, Analysis Shows
New interactive maps from MIT analyze the potential environmental and economic savings of ride-sharing in dense urban areas — in particular, the benefits of sharing taxicabs in New York City. The project, called
, uses data from 170 million trips made by New York City's 13,500 taxis in 2011. High-resolution GPS coordinates and timestamps for each trip allowed researchers to pinpoint locations in the city that are high-traffic hubs for taxi pick-ups and drop-offs, as well as calculate fare savings, decreases in total miles traveled, and cuts in CO2 emissions if ride-sharing existed. The researchers found that taxi-sharing could reduce the number of trips by 40 percent with only minimal inconvenience to the passengers. The findings highlight the potential benefits of ride-sharing in New York and other cities, including lower vehicle emissions, reduced congestion, and savings in time and money.
07 Mar 2014:
U.S. Car-Sharing Programs Have
Taken 500,000 Cars off Roads, Report Says
The rapid growth of car-sharing programs has cut the number of vehicles on U.S. roads by more than half a million, according to new research
by AlixPartners, a consultancy group with clients in the automotive industry. The trend will continue beyond 2020, the group projects, at which point 4 million people will be participating in car-sharing programs and 1.2 million fewer cars will be on the road. Of the 10 cities surveyed, residents of Boston, home of the Zipcar company, were most aware of car-sharing programs. Young people and, surprisingly, households with children were least likely to own their own cars, the survey said. Roughly half of the people who had tried car-sharing had already decided not to purchase or lease their own car, and did not plan to do so in the future. Rather than environmental concerns, nearly 60 percent of interviewees said cost and convenience led them to participate in car-sharing.
11 Feb 2014:
Shrinking Household Size
May Offset Progress in Curbing Population
Household size — the number of people living together under one roof — has been shrinking worldwide, and the trend could have major consequences for resource consumption
, new research finds
. Although global population growth has been somewhat curbed in the developed world, the number of households has continued to grow at a much faster pace in nearly all countries, Michigan State University researchers found. Average household size in developed nations declined from approximately five members in 1893 to 2.5 in 2000, while the rapid decline in household size in developing nations began around 1987, according to the research
, which analyzed trends between the years 1600 and 2000. Smaller households are typically less efficient, with fewer people using proportionally more land, water, and energy. Constructing housing units also consumes lumber and building supplies, and generally requires building more roads and commercial areas. "This will put enormous strain on the environmental life support system we rely on, even if we achieve a state of zero population growth," one study author said.
Photo Essay: In New Orleans, an
Architect Makes Water His Ally
Dutch Dialogues II
No city in the United States faces as grave a threat from flooding, hurricanes, and rising seas as New Orleans, part of which lies below sea level. But New Orleans architect David Waggonner
and his associates, learning lessons from the Dutch
, have proposed a revolutionary vision for New Orleans that seeks to make an asset of the water that surrounds the city, remaking unsightly canals into an important and scenic part of the landscape and mimicking nature to store rainfall. Waggoner’s firm has been chosen to help develop a Greater New Orleans Urban Water Plan
, a first step in what could be a multi-billion dollar project to redesign the ways in which the region co-exists with water. “To sustain the city in this difficult site in an era of rising seas and more extreme weather, we must convert our necessities into niceties, into desirable places that connect with people and culture,” Waggonner says. View the Photo Gallery
29 Jan 2014:
Driven by State Incentives
Electric Cars Top Vehicle Sales in Norway
Norwegians have been snapping up electric cars: In the last three months of 2013, the Tesla Model S and Nissan Leaf outsold all other cars, including conventionally fueled models. But rather than environmental concerns,
An EV charges up in Oslo
a host of government incentives — totaling an estimated $8,300 per vehicle — are largely driving the boom, the Guardian reports
. Norway, a country of only 5 million people, currently has around 21,000 electric vehicles (EVs) on the roads, compared to 70,000 EVs among 313 million Americans and 5,000 EVs among 63 million people in the UK. More than 1,200 EVs are being sold in Norway per month thanks to incentives that include free electricity for recharging, lower sales tax rates, waived tolls, free parking, insurance discounts, and permission to drive in bus lanes, which are less crowded. The EV rush is expected to slow, however, as bus lanes become more crowded, and the government plans to end financial incentives once 50,000 EVs are registered, which could occur by 2016.
07 Jan 2014:
Suburbs Offset Low Carbon
Footprints of Major U.S. Cities, Study Finds
City-dwellers in the U.S. have significantly smaller per-capita carbon footprints than their rural counterparts, according to new research
from the University of California, Berkeley. But the carbon-intense suburbs surrounding major cities essentially cancel out the small carbon footprints of city residents,
the study found. Vehicle emissions accounted for the majority of carbon dioxide produced in the suburbs, reflecting suburbanites' longer commutes to work, school, and stores. The study looked at 37 factors — including weather, income, home size, and transportation data — to estimate household carbon footprints. The average carbon footprint of households living in the center of large, densely populated cities is about 50 percent below the national average, while households in distant suburbs have carbon footprints up to twice the national average, according to the study published in Environmental Science & Technology
19 Dec 2013:
Los Angeles Becomes First
Major U.S. City to Adopt Cool Roof Rule
The Los Angeles City Council has voted unanimously to require "cool roofs" for all new and refurbished homes, becoming the first major U.S. city to do so
. "Cool roofs" incorporate light- and heat-reflecting building materials, which can lower the surface temperature of the roof by up to 50 degrees F on a hot day, according to Climate Resolve
, the local organization that pushed for the ordinance. Such roofs do not necessarily need to be white, the Global Cool Cities Alliance says; they can also be shades of gray, or even red. Research suggests that by mid-century temperatures in Los Angeles will increase by 3.7 to 5.4 degrees F, with the number of days above 95 degrees F tripling in the city's downtown. "The changes our region will face are significant, and we will have to adapt," said UCLA scientist Alex Hall, who led the research. The mandate will not cost homeowners additional money because of expanded incentives.
09 Dec 2013:
Intensifying Storms Are
Contributing To Ongoing U.S. Wetlands Loss
The U.S. is losing wetlands at a rate of 80,000 acres per year, in part because of intensifying coastal storms and sea level rise, according to a new government study
. From 2004 to 2009, the country lost more than 360,000 acres of freshwater and saltwater wetlands, a decline driven both by traditional factors, such as coastal development, as well as worsening storms and slowly rising seas, the study says. The rate of loss is a signal that government efforts to protect and restore wetlands are failing to keep pace with major environmental changes, experts told The Washington Post
. The most pronounced wetlands losses were along the Gulf of Mexico, where major hurricanes have wreaked havoc on coastal lands. Along the Atlantic coast, a rapid increase in coastal development is funneling stormwater runoff into wetlands that cannot handle it, the study said. The loss rate of 80,000 acres annually represents a 25 percent increase over the rate of wetlands loss during 1998-2004, the last time government agencies examined the problem.
06 Dec 2013:
China Doubles Pace
Of Renewable Energy Installation in 2013
Over the past 10 months China has added renewable energy sources to its power grid at double the pace of 2012, according to its National Energy Administration (NEA). The renewable energy push, part of a massive effort to cut air pollution in China's large cities, has added more than 36 gigawatts of clean energy capacity
Shanghai, Dec. 3, 2013
so far this year, Bloomberg News reports
. Hydroelectric power grew by 22.3 gigawatts in the first 10 months of 2013, new nuclear energy installations totaled 2.2 gigawatts, solar 3.6 gigawatts, wind 7.9 gigawatts. China's solar energy capacity could triple from 2012 levels to 10 gigawatts by the end of the year, while wind and nuclear power capacity could increase by 22 and 17 percent, respectively, the NEA said. That should offer some relief from China's choking air pollution. In Shanghai, schoolchildren were ordered indoors today
as air pollution reached extremely hazardous levels, exceeding World Health Organization health guidelines for fine particulate matter by 24 times.
05 Dec 2013:
Urban Car Use Declines
As Biking and Public Transit Rise in the U.S.
Americans in urban areas are driving less, biking more, owning fewer cars, and using public transportation more frequently, according to new research by the U.S. Public Interest Research Group
(U.S. PIRG). The number of people driving to work fell in 99 of 100 major urban areas between 2006 and 2011, and the number of miles driven by car fell in three-quarters of the cities studied over that time, the PIRG study showed. The proportion of people biking to work increased in 85 of 100 cities, while the number of miles traveled on public transit increased in 60 of 98 cities. Meanwhile, the number of people working from home grew in all 100 cities, the report said. From 2004 to 2012, the average number of vehicle-miles driven per person decreased by 7.6 percent nationwide. "There is a shift away from driving,” said Phineas Baxandall, an analyst for the U.S. PIRG Education Fund. "Instead of expanding new highways, our government leaders should focus on investing in public transit and biking for the future."
06 Nov 2013:
Disturbed Tropical Forests
Are Slow to Regain Plant Biodiversity
In tropical forests that are regrowing after major disturbances, the ability to store carbon recovers more quickly than plant biodiversity, researchers from the U.K. have found
. However, even after 80 years, recovering forests store less carbon than old-growth
A regrowing tropical forest in Brazil
forests, according to a study published in the Proceedings of the Royal Society B.
This is likely because regenerating forests are often dominated by small, fast-growing trees and it may take centuries for larger trees, which hold more carbon, to become established, according to scientists from the Center for Ecology & Hydrology and Bournemouth University, who studied more than 600 recovering tropical forests. Tree species that are hallmarks of old-growth forests were rare or missing in the regrowing forests, the study showed. Since regenerating forests are often located far from old-growth forests and surrounded by farmland, it may be difficult for animals to move seeds between the forests, which may account for the lower plant biodiversity, researchers said.
05 Nov 2013:
Beijing To Limit New Cars
By 40 Percent in Anti-Pollution Drive
In an effort to reduce severe air pollution in the Chinese capital, Beijing will limit by 40 percent the number of new cars sold annually for the next four years, cutting license plate allocations from 240,000 to 150,000 each
Chang'an avenue in Beijing
year. The cap, which should also help ease the capital's worsening traffic congestion, means Beijing will license only 600,000 new cars between 2014 and 2017 — fewer than in 2010 alone, Reuters reports
. By 2017, 40 percent of those licenses, which drivers vie for in auctions and lotteries, will be reserved for hybrid and electric cars. New car sales in China are currently capped in four cities — Beijing, Shanghai, Guangzhou, and Guiyang — and the government plans to limit sales in eight additional cities, the China Association of Automobile Manufacturers said.
30 Oct 2013:
Low on Natural Gas, China
Cities Will Face Choking Air Pollution
In a push to curb air pollution, China has been urging its cities to rely more heavily on natural gas and less on coal. But a shortage of natural gas is threatening that goal, as urban populations boom and domestic gas production lags, Reuters reports
. Chinese officials have said that to reduce air pollution the most densely populated parts of Beijing should use only gas heat, which limits the supply of natural gas for smaller cities and forces those cities to rely on coal. Pollution levels in Chinese cities commonly exceed World Health Organization guidelines by 40 to 50 times. The problem is most pronounced in northern China, where air pollution from burning coal has already shortened life expectancy by 5.5 years compared to the southern part of the country. China's natural gas shortage is expected to be 10 percent higher this year than last year, since more users have switched from coal. Authorities are rationing natural gas and prioritizing its use for homes and transportation, but experts don't expect the shortage to subside anytime soon.
28 Oct 2013:
Underground Heat From
Cities Could Help Power Them, Study Says
The heat generated by urban areas and their buildings, factories, sewers, and transportation systems could be used to power those cities, according to a new study by German and Swiss researchers
. Thermal energy produced by the so-called "urban heat island effect" warms shallow aquifers lying below cities, and geothermal and groundwater heat pumps could tap into those warm reservoirs to heat and cool buildings, the scientists say. In the southwest German city of Karlsruhe, the researchers found that the city of 300,000 generated 1 petajoule of heat per year — enough to heat 18,000 households. Karlsruhe's underground heat production increased by about 10 percent over the past three decades, the team reported in Environmental Science and Technology
. The biggest contributors to the city's underground heat flux were its densely populated residential areas and surface temperature increases associated with paving. Sewage pipes, underground district heating networks, and thermal waste water discharges also contribute to warming shallow aquifers, the study found.